It's the same as the "wicked wheel" Basically the intake wheel that was installed on the "up to" 97 PSD. What I have learned is the later PSD's have a different type of wheel and they don't work as well, but are quieter. The earlier ones whine like a semi. Install is 2-3 hours dedicated work by an experienced mechanic, more for a weekend wrench. I did mine on the engine by removing the intake housing, Y-pipe and downpipe. It's not an impossible feat but set aside a good block of time to do the job. There are some good write ups with step by step instructions, but the search is disables right now.